timing on a 3.2L with Carbs

[sundevil64]

I have a 3.2L with PMO's. Stock EFI cams (converted from EFI to PMO) and stock EFI pistons. This is a US spec motor (1984).

I am still researching timing curves. Any harm in going 32* advance at 3400rpm this would be max rpm. I have a 123 distributor I can program.

Currently, I am 7* at idle and max 27* at 3400 rpm.

Thank you in advance.

John

[sundevil64]

Good morning. Any suggestions from those with experience with this?

[cabmandone]

I'm sure Gordo2 will be chiming in as this is something he played around a lot with. But you might consider a dyno day to get things really dialed in. I know it helped Gordo with his setup.
He's running a different cam, different ignition, and has JE pistons in his car so his setup is different from yours.

[sundevil64]

Thanks Nick. I haven’t gotten to that point yet. There are some carb tuning issues going on right now that I am working through. I was running lean on acceleration but was able to improve that by pulling timing. The flat spots due to lean mixture are in the midrange. I am mew to carbs on these cars but working through it and learning. Lots of reading and experimenting.

[cabmandone]

I'll tell Gordo2 about your thread. He has done a lot of carb tuning. Good info in this thread.
http://forums.pelicanparts.com/911-engine-rebuilding-forum/821976-gordos-pmo-carb-tuning.html

[sundevil64]

Thank you Sir!

[Gordo2]

As Cabmando mentioned, I'm running a 3.2L with PMO's and Electromotive's XDi ignition.

I've found ~33° total advance provides best performance (for my engine config), adding most of the advance early / lower RPM range. XDi lets you adjust idle to 3k RPM advance and 3k on up.

Here's a link discussing some ignition tuning:
http://forums.pelicanparts.com/porsche-911-technical-forum/884610-dyno-results-gordos-3-2l.html

My engine build is rather conservative WRT cam profile and pistons which comes in around 9.4 compression ratio. The lower CR & moderate cam allows me to play with things like ignition timing with less concern of pre-ignition (as compared to a higher CR engine). Technically this config would also allow running lower grade / 87 octane fuel - but I run higher, since I tend to play with timing and other setting often.

Good luck,

Gordo

[sundevil64]

Thanks Gordo. I think �� have read some of your stuff. I will review it. I too am running a conservative setup and running 93 octane.

[cabmandone]

John,
What are you using to determine you're lean or rich? Do you have an AFR gauge? Don has an Innovate LM1 or 2 (I can't remember)handheld. I use mounted setup made by 14Point7.

[sundevil64]

I have an LM 1 on the car. When it goes flat I can see that I am lean 16-18:1 ratio.

[snbush67]

Here is a good curve to start with for your 3.2 with carburetors.

[sundevil64]

Interesting thanks! I was close. I have tried multiple scenarios some off some close. Perfect and using a 123 Dist!

[snbush67]

Originally Posted by sundevil64

Interesting thanks! I was close. I have tried multiple scenarios some off some close. Perfect and using a 123 Dist!

I am tuning my car, the curve I posted was recommended by ICARP. He also recommended that I tap into the manifolds for vacuum so I can use the MAP function in the 123. I’m planning to do that.

I think the most important thing I’ve done is install an AFR gauge.